Process for effecting injection-molded-in decoration

ABSTRACT

A decoration sheet is retained on the cavity periphery by a sheet clamp in such a state that it is projected into a molding cavity of a female die. Then the decoration sheet is heated and softened by a curved hot platen, and thereafter it is drawn through suction ports of the female die to bring the sheet into close fit to the inner periphery of the molding cavity. The deformation amount of the decoration sheet heated and softened is decreased in premolding the sheet into the molding cavity surface of the female die. Therefore, distortion of the decoration sheet, appearance of wrinkles, and breakage thereof become little. Next, the female die and the male die are coupled with each other to effect die clamping, and a molten resin is poured to fill the molding cavity to effect injection molding.

TECHNICAL FIELD

The present invention relates to a process and an apparatus foreffecting injection-molded-in foil decoration, by which foil decorationis effected on a surface of a molded body at the same time as injectionmolding thereof, and particularly, to a process and apparatus suitablyapplicable to effecting foil decoration properly on the surface of themolded body having relatively large curvature or level differences ofsurface.

BACKGROUND ART

Foil decoration is utilized so as to be effected on the surface of themolded body at the same time as injection molding of the resin moldedbody, thereby producing, for example, the molded article 13 as shown inFIG. 44, on the surface of which a pattern 11 and letters 12 are formed.A molding apparatus 10 as shown in FIG. 45 is used for theinjection-molded-in foil decoration. (See the bulletins of JapaneseLaid-open Patent Application No. 59-31130 and Japanese PatentPublication No. 4-42172.)

This apparatus 10 is provided with a female die 20 and a male die 25arranged to be opposed to the female die 20. The female die 20 has amolding cavity 21 corresponding to the contour of the molded body to beobtained and suction ports 22 passing through the inside to open to thecavity 21, and is arranged to be translated in approaching-leavingdirections relative to the male die 25 by a translating unit 23 composedof a cylinder, etc. Further, the male die 25 has a core 26, which is tobe inserted into the cavity 21, and a pouring port (gate) 27 of amolten-resin-injecting unit is formed therein. Further, a hot platen 29is arranged as movable into or away from between the female die 20 andthe male die 25. This hot platen 29 includes its front surface (on thefemale die 20 side) as a heating surface.

In order to effect foil decoration at the same time as injection moldingusing such an apparatus 10, a decoration sheet 15 is first set to beopposed to the molding cavity of female die 20, and the decoration sheet15 is heated to soften by the hot platen 29 (FIG. 45). Then thedecoration sheet 15 is pinched between the female die 20 and the hotplaten 29 so as to close an opening face of the cavity 21, the cavity isevacuated through the suction ports 22 formed in the female die 20, andcompressed air is supplied through an air vent (not shown) provided inthe hot platen 29 as occasion demands.

It makes the decoration sheet 15 stretched along the inner periphery ofcavity 21 as adhering thereto in fit, as shown in FIG. 46. Here, thisstep is generally called as premolding.

Next, after the hot platen 29 is withdrawn from between the both dies,as shown in FIG. 47, the female die 20 is advanced to be coupled withthe male die 25, thereby effecting clamping of the dies. Thereafter,into a cavity space formed between the female die 20 and the male die25, a molten resin is poured and charged through the pouring port 27 ofthe injecting unit provided in the male die 25, thereby effectinginjection molding.

Thus, the decoration sheet 15 in the female die 25 becomes integratedwith the resin injected (molded body P) to adhere thereto. When the diesare opened after completion of injection molding, the molded body can betaken out of the dies as the decoration sheet is adhered to the outersurface.

Here, if the decoration sheet 15 is a bonded and layered film (laminatefilm), the foil decoration is completed at that stage, and all layers ofthe decoration sheet 15 are adhered to integrate onto the outer surfaceof the molded body P to form a decorative layer. On the other hand, ifthe decoration sheet 15 is a transfer film, only a base film of thedecoration sheet 15 integrated onto the outer surface of the molded bodyP is released in a later step, so that a transfer layer such as apattern layer is left on the molded body P side to form a decorativelayer, thereby completing the foil decoration.

Since in the conventional processes for effecting injection-molded-infoil decoration the decoration sheet is set on the opening surface sideof the molding cavity in the female die and then is pushed into themolding cavity by evacuation or by the core member, whereby the sheet isdrawn toward the cavity inner periphery (cavity surface) at a stretch ina short period of time to become laid along it, the decoration sheet hasto be stretched at high speed in the mold cavity. Stretching amounts ofthe decoration sheet in the dies become larger as the level differenceor curvature of the surface of molded body becomes greater. Further, ifthe sheet is stretched at high speed, distribution of stresses cannot besufficiently dispersed or relaxed, which causes the stretching amountsto be concentrated locally. When the decoration sheet is locallystretched to a large extent, the pattern layer or the like formedthereon is naturally stretched as well, which could result in distortingthe pattern layer to an unignorable extent or which could causepositional deviation between the pattern of the decoration sheet and theconcave or convex contour of the molded body, thus failing to achievedesired foil decoration on the surface of molded body. In an extremecase, wrinkling or breakage may occur.

The problems caused by the stretching of the decoration sheet can beavoided to some extent by preliminarily heating to soften the decorationsheet by the hot platen as described above; but, even in that case, if amolded body had large level differences or curvature of surface,wrinkles or distortion would tend to appear because of increase of thestretching and drawing amounts of the decoration sheet. Therefore, itwas difficult to effect foil decoration as expected. Further, if thestretching speed is decreased to relief the stress in order to deformthe heated and softened decoration sheet in large stretching and drawingamounts, strain deformation of the sheet becomes distinct in this casebecause of its own weight or the like during a period before it reachesthe cavity surface.

SUMMARY OF THE INVENTION

Under such circumstances, an object of the present invention is toprovide a process for effecting injection-molded-in foil decoration inwhich foil decoration can be suitably effected on a molded body havinglarge level differences and curvature of the surface without substantialdistortion, position shift, and the like, and its apparatus.

A first feature of the present invention is a process for effectinginjection-molded-in foil decoration, comprising the steps of retaining adecoration sheet relative to a female die so that the decoration sheetis curved substantially along a surface of a cavity of the female die;heating the decoration sheet retained relative to the female die by ahot platen to soften the decoration sheet; bringing the decoration sheetinto close fit to the surface of the cavity; coupling the female diewith a male die to clamp the dies; and effecting injection molding bypouring and filling a molten resin between the female die and the maledie, thereby adhering the decoration sheet to an injection moldedarticle.

A second feature of the present invention is a process for effectinginjection-molded-in foil decoration, comprising the steps of: retaininga decoration sheet relative to a female die so that the decoration sheetis curved substantially along a surface of a cavity of the female die;heating the decoration sheet retained relative to the female die by aflexible sheet heating body to soften the decoration sheet; bringing thedecoration sheet into close fit to the surface of the cavity; couplingthe female die with a male die to clamp the dies; and effectinginjection molding by pouring and filling a molten resin between thefemale die and the male die, thereby adhering the decoration sheet to aninjection molded article.

A third feature of the present invention is a process for effectinginjection-molded-in foil decoration, comprising the steps of:introducing a decoration sheet so that the sheet is curved substantiallyalong a surface of a cavity of a female die; retaining the decorationsheet relative to the female die in such a curved state as to besubstantially along the surface of the cavity thereof; heating thedecoration sheet retained relative to the female die by heating means tosoften the sheet; bringing the decoration sheet into close fit to thesurface of the cavity; coupling the female die with a male die to clampthe dies; and effecting injection molding by pouring and filling amolten resin between the female die and the male die, thereby adheringthe decoration sheet to an injection molded article.

A fourth feature of the present invention is an apparatus for effectinginjection-molded-in foil decoration, comprising: a female die having asurface of a cavity; a male die arranged to be opposed to the female diewith a decoration sheet inbetween and having a resin pouring port; asheet clamp having a periphery stop frame which is in contact with theperiphery of the cavity of the female die and a sheet stop frame,attached to the periphery stop frame, for keeping the decoration sheetcurved substantially along the surface of the cavity, for retaining thedecoration sheet inside the cavity; a hot platen for heating thedecoration sheet retained relative to the female die by the sheet clamp;moving means for moving the sheet clamp and the hot platen each relativeto the female die; and sheet supply means for supplying the decorationsheet to the cavity surface side of the female die.

A fifth feature of the present invention is an apparatus for effectinginjection-molded-in foil decoration, comprising: a female die having asurface of a cavity and a suction port opening at the surface of thecavity; a male die arranged to be opposed to the female die, and havinga resin pouring port; a sheet clamp having a projection which makes adecoration sheet curved substantially along the surface of the cavity,for retaining the decoration sheet in cooperation with the periphery ofthe cavity; and sheet supply means for supplying the decoration sheet tothe cavity surface side of the female die, wherein a curved slit isformed in said sheet clamp, a sheet heating body is inserted into theslit in the sheet clamp, and the sheet heating body is curved in theslit substantially in the same shape as that of the decoration sheetretained by the sheet clamp.

A sixth feature of the present invention is an apparatus for effectinginjection-molded-in foil decoration, comprising: a female die having asurface of a cavity and a suction port opening at the surface of thecavity; a male die arranged to be opposed to the female die, and havinga resin pouring port; a sheet clamp having a projection which makes adecoration sheet curved substantially along the surface of the cavity,for retaining the decoration sheet in cooperation with the periphery ofthe cavity; and sheet supply means for supplying the decoration sheet tothe cavity surface side of the female die, wherein a frame body forhousing and holding a sheet heating body, in which a curved slit isformed, is provided on an opposite side to the female die with respectto said sheet clamp, the sheet heating body is inserted into the slit ofthe frame body for housing and holding the sheet heating body, and thesheet heating body is curved in the slit substantially in the same shapeas that of the decoration sheet retained by the sheet clamp.

A seventh feature of the present invention is an apparatus for effectinginjection-molded-in foil decoration, comprising: a female die having asurface of a cavity and a suction port opening at the surface of thecavity; a male die arranged to be opposed to the female die, and havinga resin pouring port; a sheet clamp having a curved projection, forretains a decoration sheet in cooperation with the periphery of thecavity of the female die; sheet supply means for supplying thedecoration sheet to the cavity side of the female die; and heating meansfor heating the decoration sheet; wherein said female die is providedwith a curved recess corresponding to the projection of said sheetclamp, a pair of sheet guide grooves are provided on a surface of thecurved recess, and sheet pinching means for pinching the both side edgesof the decoration sheet is moved along the sheet guide grooves.

According to the first feature, after retaining the decoration sheetrelative to the female die so that the decoration sheet is curvedsubstantially along the surface of the cavity thereof, the decorationsheet is heated and softened by the hot platen and then is brought intoclose fit to the surface of the cavity, whereby the decoration sheet cansmoothly be brought into close fit to the surface of the cavity.

According to the second feature, after retaining the decoration sheetrelative to the female die so as that the decoration sheet is curvedsubstantially along the surface of the cavity thereof, the decorationsheet is heated and softened by the flexible sheet heating body and thenis brought into close fit to the surface of the cavity, whereby thedecoration sheet can smoothly be brought into close fit to the surfaceof the cavity.

According to the third feature, after introducing the decoration sheetso that the decoration sheet is curved substantially along the surfaceof the cavity of the female die and retaining the decoration sheet inthis state, the decoration sheet is heated and softened by the heatingmeans, whereby the decoration sheet can smoothly be brought into closefit to the surface of the cavity.

According to the fourth feature, the decoration sheet is curvedsubstantially along the surface of the cavity by the sheet stop frame ofthe sheet clamp and is retained by the periphery stop frame so as to bein contact with the periphery of the cavity, and then the decorationsheet is heated and brought into close fit to the surface of the cavity,whereby the decoration sheet can smoothly be brought into close fit tothe surface of the cavity.

According to the fifth feature, the decoration sheet is curvedsubstantially along the surface of the cavity by the sheet clamp havingthe projection, and the sheet heating body is inserted into the slit ofthe sheet clamp and is curved substantially in the same shape as that ofthe decoration sheet retained by the sheet clamp to heat the decorationsheet, whereby the decoration sheet can uniformly be heated and smoothlybe brought into close fit to the surface of the cavity.

According to the sixth feature, the decoration sheet is curvedsubstantially along the surface of the cavity by the sheet clamp havingthe projection, the sheet heating body is inserted into the slit of theframe body for housing and holding the sheet heating body, and the sheetheating body is curved substantially in the same shape as that of thedecoration sheet retained by the sheet clamp, whereby the decorationsheet can uniformly be heated and smoothly be brought into close fit tothe surface of the cavity.

According to the seventh feature, the sheet pinching means for pinchingthe both side edges of the decoration sheet runs in the pair of sheetguide grooves of the female die, whereby the decoration sheet can beintroduced along the surface of the curved recess of the female die.Then the decoration sheet is retained and heated so as to be broughtsmoothly into close fit to the surface of the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing to show an apparatus for effectinginjection-molded-in foil decoration in the first embodiment of thepresent invention.

FIG. 2 is a detail view of a curved hot platen shown in FIG. 1.

FIG. 3 is a drawing to illustrate a step for effecting foil decorationat the same time as injection molding, using the apparatus for effectinginjection-molded-in foil decoration in FIG. 1.

FIG. 4 is a drawing to illustrate a step of clamping a decoration sheetand heating it by the curved hot platen.

FIG. 5 is a drawing to illustrate a step of effecting suction fitting ofthe softened decoration sheet onto the inner periphery of a moldingcavity in a female die.

FIG. 6 is a drawing to illustrate an injection molding step.

FIG. 7 is a drawing to illustrate a step of taking a foil decorationmolded body out.

FIG. 8A is a drawing to show a molded article in which a decorationsheet is a bonded and layered film.

FIG. 8B is a drawing to show a molded article in which a decorationsheet is a transfer film.

FIG. 9 is a drawing to show another example of the molded body.

FIG. 10 is a schematic drawing to show another embodiment of the sheetclamp.

FIG. 11 is a schematic drawing to show another embodiment of the curvedhot platen.

FIG. 12 is a drawing to show another example of the foil decorationmolded article.

FIG. 13 is a schematic drawing to show another embodiment of theapparatus for effecting injection-molded-in foil decoration.

FIG. 14 is a schematic drawing to show another embodiment of the sheetclamp.

FIG. 15 is a drawing to illustrate the operation of the sheet clamp ofFIG. 14.

FIG. 16 is a schematic drawing to show another embodiment of the curvedhot platen.

FIG. 17 is a drawing to illustrate a method for mounting a hot platenblock unit to a base.

FIG. 18A is a drawing to illustrate the hot platen block unit.

FIG. 18B is a drawing to illustrate the hot platen block unit.

FIG. 19 is a schematic drawing to show an apparatus for effectinginjection-molded-in foil decoration in the second embodiment of thepresent invention.

FIG. 20 is a perspective view of a sheet clamp frame shown in FIG. 19.

FIG. 21 is a drawing to illustrate a guide rail for a sheet heatingbody.

FIG. 22 is a drawing to illustrate a step of inserting a flexible sheetheating body into the sheet clamp.

FIG. 23 is a drawing to illustrate the step of inserting the flexiblesheet heating body into the sheet clamp.

FIG. 24 is a drawing to illustrate a step of heating and softening thedecoration sheet.

FIG. 25 is a drawing to illustrate a step of clamping the female andmale dies.

FIG. 26 is a drawing to illustrate a step of opening the female and maledies.

FIG. 27 is a drawing to illustrate another embodiment of the presentinvention.

FIG. 28 is a drawing to illustrate another embodiment of the presentinvention.

FIG. 29 is a schematic perspective view to show an apparatus foreffecting injection-molded-in foil decoration in the third embodiment ofthe present invention.

FIG. 30 is an operational drawing of the apparatus for effectinginjection-molded-in foil decoration according to the present invention.

FIG. 31 is an operational drawing of the apparatus for effectinginjection-molded-in foil decoration according to the present invention.

FIG. 32 is an operational drawing of the apparatus for effectinginjection-molded-in foil decoration according to the present invention.

FIG. 33 is an operational drawing of the apparatus for effectinginjection-molded-in foil decoration according to the present invention.

FIG. 34 is an operational drawing of the apparatus for effectinginjection-molded-in foil decoration according to the present invention.

FIG. 35 is a perspective view to show sheet pinching means.

FIG. 36 is a sectional view to show the operation of the sheet pinchingmeans.

FIG. 37 is a sectional view to show the operation of the sheet pinchingmeans.

FIG. 38 is a sectional view to show the operation of the sheet pinchingmeans.

FIG. 39 is a perspective view to show such a state that the female dieis in contact with the sheet clamp.

FIG. 40 is a perspective view to show such a state that the decorationsheet is heated by the sheet heating body.

FIG. 41 is a perspective view to show such a state that the sheetheating body is pulled up from the sheet clamp.

FIG. 42 is a perspective view to show such a state that the female die,the sheet clamp, and the male die are clamped.

FIG. 43A is a drawing to show a modification of a feed mechanism of thesheet pinching means.

FIG. 43B is a drawing to show the modification of the feed mechanism ofthe sheet pinching means.

FIG. 44 is a drawing to shown a molded article obtained by the processfor effecting injection-molded-in foil decoration.

FIG. 45 is an operational drawing of the conventional apparatus foreffecting injection-molded-in foil decoration.

FIG. 46 is an operational drawing of the conventional apparatus foreffecting injection-molded-in foil decoration.

FIG. 47 is an operational drawing of the conventional apparatus foreffecting injection-molded-in foil decoration.

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

The first embodiment of the present invention will be described indetail below with reference to the drawings.

FIG. 1 is a schematic drawing to show an example of the apparatus foreffecting injection-molded-in foil decoration of the present embodiment.The apparatus of the present invention comprises a female die 30 similarto that in the conventional example and a male die 40 arranged to beopposed to the female die 30. The female die 30 is provided with acavity 31 having a cavity surface 31a corresponding to the contour of amolded body to be molded and a plurality of suction ports 32 formedinside the female die 30 and opening on the cavity surface 31a. Thesuction ports 32 are connected to an unrepresented vacuum pump through asuction tube 33. The male die 40 is fixed to a stationary platen 44, andthe female die 30 is connected to a pressure ram 35 through a movingplate 34, whereby the female die 30 is arranged as movable relative tothe male die 40. Further, the male die 40 has a core 41 which is to beinserted into the molding cavity 31 of the female die 30, as in theconventional case, and a pouring port (pouring gate) 47 of amolten-resin-injecting unit is formed inside thereof.

A sheet clamp 50 and a curved hot platen 60 are arranged as movable intoor away from between the female die 30 and the male die 40, and adecoration sheet 15 is passed through between the female die 30 and thesheet clamp 50.

The sheet clamp 50 is made of, for example, a stainless steel plate,etc. and has a periphery stop frame 52, which comes into contact withthe outer periphery of the molding cavity 31 of the female die 30, andsheet stop frames 54 fixed to the periphery stop frame 54 and projectinginto the molding cavity while used. The sheet stop frames 54 have alevel difference smaller than that of the cavity surface 31a and acurvature equal to or smaller than that of the cavity surface 31a, and,as described below, retain the decoration sheet 15 in such a state as tobe pushed into the cavity 31.

Here, the level difference ΔD of the cavity surface 31a of the femaledie 30 is defined as a depth of the deepest point of a recessed portionof the cavity surface 31a measured from the level of a parting plane 36in the case that the female die 30 has a recessed cavity surface 31a asin FIG. 1. On the other hand, in the case that the female die 30 has aprojecting cavity surface 31a as in FIG. 13, it is defined as a heightof the highest point of a projecting portion of the cavity surface 31ameasured from the level of the parting plane. A level difference Δd ofthe decoration sheet 15 is defined as a difference of elevation from theflat portion of the sheet to the highest portion or the deepest portionof the decoration sheet 15. In the present invention, ΔD>Δd.

FIG. 1 shows two sheet stop frames 54 at positions corresponding to theboth ends of the cavity 31, but without necessarily having to be limitedto two, the number may be three or more according to the size, thedepth, the shape, etc. of the cavity surface 31a. The sheet clamp 50 isfixed to a rod 56 of an air cylinder 55, whereby it is arranged to beput in and out between the female die 30 and the male die 40 by the aircylinder 55 and is also arranged as movable in the directions toapproach and leave the female die 30 through an unrepresented drivingmechanism.

The curved hot platen 60 has a plurality of sheet heating bodies 62,which are fixed to a surface of a hot platen main body 61 by screws 63,and the surface on the side of the female die 30 is a heating surface,as shown in detail in FIG. 2. An electric current is supplied to thesheet heating bodies 62 from an unrepresented power supply through aline 64, so that the entire surface uniformly generates heat by heatersburied inside. The curved hot platen 60 is also fixed to a rod 66 of anair cylinder 65, and it is so arranged as to be put in and out betweenthe female die 30 and the male die 40 and as to be movable in thedirections to approach and leave the female die 30 by an unrepresenteddriving mechanism in the same manner as the sheet clamp 50.

Next described is a process for effecting foil decoration at the sametime as injection molding, using the apparatus of the presentembodiment.

As shown in FIG. 3, the decoration sheet 15 is drawn out from a feedroll 71 through lead-on rolls 72, 72 so as to run in front of the femaledie 30. The front end of the decoration sheet 15 is pulled in the arrowdirection by an unrepresented means so that the decoration sheet 15 maybe kept not loosened. Desired patterns are printed at a predeterminedpitch on the decoration sheet 15. In the case that the sheet is either areverse printing bonded and layered sheet or a transfer sheet, theprinted surface is set on the opposite side to the female die 30; in thecase of a normal printing bonded and layered sheet, the printed surfaceis set on the side of the female die 30. Further, positioning marks 17(for example, register marks, cross marks, rectangles, stripes, etc.)are printed at a predetermined pitch or in an endless manner (as stripepatterns) on the decoration sheet 15 together with the patterns.

First, in such a state that the sheet clamp and the curved hot platenare withdrawn from between the female and male dies 30, 40, thedecoration sheet 15 is unwound by a length of one shot from the feedroll 71 through the lead-on rolls 72, 72. This one-shot unwinding andpositioning of a pattern relative to the female die 30 is completed bystopping the drive of the sheet when a position sensor 75 such as aphototube detects the mark 17 on the sheet. In order to enablepositioning in the longitudinal and lateral directions of the decorationsheet 15, it is ordinary practice to set vertical and horizontal pairsof position sensors, for example.

Further, if the patterns on the decoration sheet 15 are a whole-area,single-colored pattern which does not require positioning, thepositioning step may be omitted.

Next, the sheet clamp 50 and the curved hot platen 60 are introducedbetween the female die 30 and the male die 40. Then the sheet clamp 50is driven to approach the female die 30, so that the decoration sheet 15is clamped on the periphery of the molding cavity of the female die bythe periphery stop frame 52, as shown in FIG. 4. The decoration sheet 15is pushed in the cavity 31 by the curved stop frames 54 of the sheetclamp 50, and is deformed and retained in a shape projecting on the sideof the cavity 31 in such a state that the level difference of thedecoration sheet is smaller than that of the cavity surface and that thecurvature of the decoration sheet 15 is equal to or smaller than that ofthe cavity surface 31a. At this time, the cavity surface 31a is closedby the decoration sheet 15, which makes such a state that a spaceisolated from the atmospheric pressure is formed in a step of reducingthe pressure inside the cavity 31 as described below. The curved stopframes 54 of the sheet clamp 50 are designed in such shape, curvature,or the like as not to cause a wrinkle or breakage of the decorationsheet 15 deformed as projected in the cavity 31 when pushed, beforeheating to soften.

While the decoration sheet 15 is clamped on the periphery of the moldingcavity 31 of the female die, the curved hot platen 60 is introducedbetween the female and male dies 30, 40, or it is further moved closerto the decoration sheet 15 clamped, as shown by the dashed line, wherebythe entire surface of the decoration sheet 15 is uniformly heated andsoftened. The surface shape of the heating surface of the curved hotplaten 60 is the same or substantially the same as that of thedecoration sheet 15 which is deformed and retained in the projectingstate into the cavity 31 by the sheet clamp 50. The decoration sheet 15may be heated mainly by radiation heat in a non-contact state in which aspace ΔL between the curved hot platen 60 and the decoration sheet 15deformed and retained is set as ΔL>0 and while each portion of thedecoration sheet 15 is kept substantially at an equal distance relativeto the hot platen surface; or the decoration sheet 15 may be heatedmainly by heat conduction in a state of ΔL=0 in which the decorationsheet 15 is kept in close fit to the surface of the hot platen 60. Inthis case, if portions of the decoration sheet 15 in contact with thesheet stop frames 54 of the sheet clamp 50 are heated less behind thestop frames 54 than the other portions, another heater may be added tothe sheet stop frames 54 to auxiliarily heat the portions.

In either case, the curved hot platen 60 of the present invention hasthe heating surface, which is of the same shape or of substantially thesame shape as the surface shape of the decoration sheet 15 retained bythe sheet clamp 50 in a state where the sheet 15 projects into themolding cavity 31, whereby the entire surface of the decoration sheet 15can be uniformly heated and softened.

Then, as shown in FIG. 5, a vacuum pump is operated so as to evacuateinside the molding cavity 31 of the female die 30 through the suctionports 32, whereby the softened decoration sheet 15 retained by the sheetclamp 50 is drawn toward the cavity surface 31a of the molding cavity 31into close fit therewith. Further, if necessary, exhaust ports may beformed in the surface of the hot platen 60 to blow compressed airtherethrough at this moment, thereby assisting the close fitting of thedecoration sheet 15 to the cavity surface 31a of the female die 30.

According to the premolding step of the present invention, thedecoration sheet 15 is preliminarily made to be projected and deformedin the molding cavity 31 of the female die 30 by the sheet clamp 50, thedecoration sheet 15 is heated and softened in that state, and thereaftera molten resin reaches up to the molding cavity surface 31a. Thisdecreases a deformation amount (stretching amount) of the softeneddecoration sheet 15 and a stretching speed when the sheet is drawn intoclose fit to the cavity surface 31a, which can reduce distortion,wrinkles, and breakage of the decoration sheet 15, and positionaldeviation between the pattern and the contour of the molded article.

After completion of the premolding as described above, the sheet clamp50 and the curved hot platen 60 are moved in the leaving direction fromthe female die 30 and are withdrawn from between the female and maledies 30, 40. Then, as shown in FIG. 6, after the female and male dies30, 40 are clamped by the pressure ram 35, the molten resin is poured tofill in the cavity 31 through the pouring port 47 of the injecting unitformed in the male die 40, thus injection molding is performed.

The injected resin may be a resin solution which is cured by a chemicalreaction, such as a polyurethane using an isocyanate as a curing agentor an unsaturated polyester using an isocyanate, an organic sulfonate,or the like as a curing agent in addition to a fluidized thermoplasticresin as heat-melted, such as a polyvinyl chloride, a polystyrene, anABS resin, an acrylic resin, or a polycarbonate.

The injected resin is cooled and solidified in this state, whereby thedecoration sheet 15 in the female die 30 comes to integrate and adhereto the injected resin.

Next, as shown in FIG. 7, the female and male dies 30, 40 are opened torelease a molded body Q with foil decoration from the dies 30, 40. Here,if the decoration sheet 15 is a bonded and layered film (laminate film),the foil decoration is already effected as it is, and all the layers ofthe decoration sheet 15 are adhered to be integrated onto the surface ofthe molded body Q to form a decorative layer (FIG. 8A). On the otherhand, if the decoration sheet 15 is a transfer film, only a base sheet15a of the decoration sheet 15 integrated on the surface of the moldedbody Q is peeled off in a later step so that a transfer layer 15bincluding a pattern layer etc. may be left on the molded body Q side toform a decorative layer, thereby completing the foil decoration (FIG.8B).

Immediately after the die opening, the molded body Q often remainsadhering to the cavity surfaces of the female die 30 or the surface ofthe male die 40. In order to release the molded body Q adhering from thedies 30, 40, thereby certainly bringing it into the state of FIG. 7, aknown ejector is used to facilitate release from the dies 30, 40, thoughit is not shown. As an example of the ejector, a slide rod may be set ascapable of being projected and withdrawn in the male die 40 or thefemale die 30, which is projected after the die opening to release themolded body Q from the dies 30, 40. In the steps except for thereleasing step, the slide rod is kept as withdrawn to such a positionthat the top surface thereof is located at the same level as the surfaceof the dies 30, 40.

Here, the hot platen main body 61 is not necessarily of asemicylindrical shape as shown in FIG. 2 as long as the shape of theheating surface of the curved hot platen 60 may be similar to the shapeof the decoration sheet 15 deformed and retained by the sheet clamp 50.For example, the hot platen main body 61 may be a curved plate-likemember and a heat-generating panel may be stuck on the surface thereof.

Modification 1

Described is an embodiment in which the foil decoration is effectedsimultaneously on a curved side surface 81 and end faces 82, 83 of amolded body 80 as shown in FIG. 9.

In this embodiment, the shape of the molding cavity of the female die 30and the shape of the male die 40 are naturally required to match theshape of the molded body 80, but the fundamental structure of apparatusis the same as shown in FIG. 1. Namely, the sheet clamp 15 and thecurved hot platen 60 are arranged as movable into or away from betweenthe female die 30 and the male die 40.

As shown in FIG. 10, the sheet clamp 50 has a periphery stop frame 86and two curved stop frames 87a, 87b extending therefrom substantially inan arc shape, and the two curved stop frames 87a, 87b are arranged so asto come closer to each other as approaching the center of the stop frame52. By corresponding the stereoscopic shape of the curved stop frames87a, 87b of the sheet clamp 50 to the ridges 84, 85 of the molded body80 in this manner, the decoration sheet 15 can be made to project intothe cavity 31 of the female die 30 so as to be deformed and retained insuch a state that the level difference thereof is smaller than the leveldifference ΔD of the molding cavity surface 31a, that the curvaturethereof is smaller than or equal to the curvature of the cavity surface31a, and that the shape is corresponding to that of the cavity surface31a. It is a matter of course that the degree of projection of thecurved stop frames 87a, 87b from the periphery stop frame 86 has to bedetermined within the range not causing wrinkles or breakage of thesheet to be deformed thereby, before softening.

Further, as schematically shown in FIG. 11, the curved hot platen 60 isformed in such a manner that sheet heating bodies 88, 89 are attachedaround the hot platen main body 61 so that the heating surface may havesubstantially the same surface shape as that of the decoration sheet 15deformed and retained by the sheet clamp 50. In this embodiment, thesheet heating bodies 88, 89 are provided not only on the curved sidesurface, but also on the other two surfaces. This curved hot platen 60may be arranged to heat the decoration sheet 15 deformed and retained bythe sheet clamp 50 mainly by heat conduction as kept in contact with theentire surface of the sheet 15, or to heat it mainly by radiation heatas keeping substantially constant the distance between the decorationsheet 15 and the surface of the curved hot platen 60, similarly as inthe previous embodiment.

The decoration sheet 15 softened by heating is drawn to adhere to thecavity surface 31a by evacuating the inside of the molding cavity 31through the suction ports 32 formed in the female die 30 as in theprevious embodiment.

According to the premolding of the present embodiment, the sheet clamp50 preliminarily deforms the decoration sheet 15 into the shapeaccording to that of the molding cavity 31 so as to make it project intothe cavity 31 of the female die 30, whereby the deformation amount ofthe decoration sheet 15 when drawn to adhere to the cavity surface 31abecomes small, which can reduce distortion, wrinkles and breakage of thedecoration sheet 15, and positional deviation between the pattern andthe contour of the molded article.

The steps after the premolding are the same as those previouslydescribed, and the detailed description thereof is omitted herein.

Modification 2

Produced was a molded article 99 with foil decoration having a curvedshape as shown in FIG. 12 and having decoration on the inside surface.This molded article with foil decoration is used as an interior memberfor automobile.

The structure of the apparatus for effecting injection-molded-in foildecoration of the present embodiment is schematically shown in FIG. 13.In the apparatus of the present embodiment, a molding cavity surface 98of a female die 30a is a projecting surface, different from theapparatus in the previous embodiment. A sheet clamp 90 has a curved stopframe 91 having the shape substantially similar to the curved shape ofthe molding cavity surface 98 of the female die and an auxiliary clamp92, which is arranged as movable into or away from between the femaledie 31a and the decoration sheet 15. A curved hot platen 95 is composedof a curved plate-like main body 96 and a sheet heating body 97 attachedonto the surface thereof on the female die side, and is arranged asmovable into or away from between the female die 30a and the male die40a in the same manner as the sheet clamp 90. The surface shape of thesheet heating body 97 is substantially the same as that of thedecoration sheet 15 deformed and retained by the sheet clamp 90.Accordingly, the heating surface of the curved hot platen 95 of thepresent embodiment is a recessed surface.

Next described is a process for producing the molded article with foildecoration as shown in FIG. 12 by effecting foil decoration at the sametime as injection molding, using the apparatus as shown in FIG. 13.

The sheet clamp 90 is introduced into between the female die 30a and thedecoration sheet 15 as the female die 30a is kept as moved to the leftof the drawing by the pressure ram 35. The decoration sheet 15 is drivenby the lead-on rolls 72 out from the feed roll 71 to run in front of thesheet clamp 90. The decoration sheet 15 is pulled in the arrow directionby an unrepresented means so as not to be loosened. Desired patterns areprinted at a predetermined pitch on the sheet 15. If the sheet is areverse printing bonded and layered film or a transfer sheet, itsprinting surface is set on the opposite side to the female die 30a; ifit is a normal printing sheet, the printing surface is set on the sideof the female die 30a. Further, marks 17 (for example, register marks,cross marks, etc.) are printed at a predetermined pitch on thedecoration sheet 15 together with the patterns.

Next, the decoration sheet 15 is unwound by a length of one shot by thelead-on rolls 72 from the feed roll 71. The one-shot unwinding andpositioning of a pattern relative to the female die 30a is effected bystopping the drive of the sheet when the position sensor 75 such as aphototube detects the positioning mark 17 on the sheet. After completionof the positioning of the sheet 15, the sheet 15 is fixed on the curvedstop frame 91 of the sheet clamp 90 by the auxiliary clamp 92. Theauxiliary clamp is, for example, a stick member attached to the sheetclamp 90 as to be rotatable, and the sheet 15 may be fixed between thestop frame 91 and the auxiliary clamp 92. Thus, the sheet 15 is deformedand retained by the curved stop frame 91 of the sheet clamp 90 in theshape substantially similar to the molding cavity surface 98. Further,this positioning step can be omitted, if the patterns of the decorationsheet 15 are a single-colored pattern over the entire surface, whichdoes not require positioning.

Next, the curved hot platen 95 is introduced into between the female die30a and the male die 40a and then is moved toward the decoration sheet15 retained by the sheet clamp 90, whereby the entire surface of thedecoration sheet 15 is uniformly heated and softened. The surface shapeof the heating surface of the curved hot platen 95 is the same orsubstantially the same as the surface shape of the decoration sheet 15deformed and retained in the projecting state in the cavity by the sheetclamp 90. In order to effect premolding and adhesion of the softeneddecoration sheet 15 onto the female cavity surface 98 withoutdestruction of the shape of the sheet, heating of the decoration sheet15 by the curved hot platen 95 may employ either one of the followingways: the decoration sheet 15 softened is heated as fixedly retained onthe hot platen 95 to be brought into contact with the female die 30a; asheet stop periphery wall is provided in the peripheral portion of thesurface of the hot platen 95 so as to heat the decoration sheet 15mainly by radiation heat as kept at a nearly constant distance to thesurface of the hot platen 95 in a non-contact state; the decorationsheet 15 is heated mainly by heat conduction as the sheet is drawn intocontact with the surface of the hot platen through the suction ports.Since the curved hot platen 95 has the heating surface which is the sameor substantially the same as the surface shape of the decoration sheet15 deformed and retained by the sheet clamp 90, the entire surface ofthe sheet can be uniformly heated and softened.

Another arrangement may be constructed, as described below, in such amanner that the sheet clamp 90 is fixed to a slide rod attached to thefemale die 30a, the male die 40a is closed while the sheet clamp 90pushes the sheet 15 against the female die 30a (as keeping only the hotplaten withdrawn), and then injection molding is performed.

Next, fixing of the sheet 15 to the sheet clamp 90 is released byreleasing the auxiliary clamp 92, and the sheet clamp 90 and the curvedhot platen 95 are withdrawn from between the female die 30a and the maledie 40a. Then the female and male dies 30a, 40a are closed by thepressure ram 35 so as to seal the inside of the molding cavity 98, andthereafter the vacuum pump connected to the suction ports in the femaledie 30a is operated to draw the softened sheet into close fit with thesurface 98 of the molding cavity. Thereafter, a molten resin is pouredto fill in the molding cavity through the pouring port 47 of theinjecting unit formed in the male die 40a, thereby effecting injectionmolding.

Modification 3

Described referring to FIG. 14 and FIG. 15 is another embodiment of thesheet clamp used in the apparatus for effecting injection-molded-in foildecoration according to the present invention.

The sheet clamp 100 of the present embodiment is different from thesheet clamp 50, 90 in the previous embodiment in that it is fixed toslide rods 102 set in the female die 30b and thus, it is incorporatedwith the female die 30b. The sheet clamp 100 is driven away from thesurface 125 of the female die 30b toward the male die 40b by the sliderods 102, and vice versa, as shown by the arrow in the drawing. Asuction groove 104 of line is formed around the molding cavity surface125 of the female die 30b and an O ring 105 is set outside the groove.The suction groove 104 is connected to an external evacuating apparatusthrough a suction path running inside the female die 30b.

As shown in FIG. 15, the decoration sheet 15 runs between the female die30b and the sheet clamp 100. The slide rods are retracted inside thefemale die 30b when the decoration sheet 15 is clamped, and they aredriven by an unrepresented driving mechanism to project out from thefemale die 30b when clamping is released.

In the case that the surface 125 of the molding cavity 31b of the femaledie 30b is of a recessed shape as shown in FIG. 14, the sheet clamp 100pushes the decoration sheet 15 to the molding cavity periphery andbecomes a part of the female die 30b, that is, forms the periphery ofthe molding cavity, as retaining the sheet 15 in desired shape andcurvature. Seal between the female die 30b and the decoration sheet 15is kept by the O ring 105. The decoration sheet 15 deformed and retainedby a stop frame 101 of the sheet clamp 100 is heated and softened by theunrepresented curved hot platen introduced into between the female die30b and the male die 40b. The shape of the heating surface of the curvedhot platen is designed to be substantially the same as the curved shapeof the decoration sheet 15 retained as deformed. The decoration sheet 15may be heated by the curved hot platen mainly by radiation heat in anon-contact state where the distance between the decoration sheet 15 andthe curved hot platen surface is kept substantially constant, or mainlyby heat conduction in such a state that the decoration sheet 15 is keptin close fit to the curved hot platen surface.

The heated and softened decoration sheet 15 is drawn to adhere to themolding cavity surface 125 by evacuating the inside of the moldingcavity surface 125 through the line suction groove 104 connected to thevacuum pump. Thereafter, the curved hot platen is withdrawn, the femaledie 30b and the male die 40b are clamped, and the molten resin is pouredto fill inside the molding cavity through the pouring port 47 of theinjecting unit formed in the male die 40b, thus injection molding isperformed.

Also in the present embodiment, because the heating surface of thecurved hot platen is the same or substantially the same as the surfaceshape of the decoration sheet 15 fixed by the sheet clamp 100, theentire surface of the decoration sheet 15 can be uniformly heated andsoftened. Further, the decoration sheet 15 is preliminarily deformed bythe sheet clamp 100 so as to project into the molding cavity surface 125of the female die 30b, whereby the deformation amount of the decorationsheet 15 becomes small when drawn into close fit to the molding cavitysurface 125, which in turns decreases distortion, wrinkles, and breakageof the decoration sheet 15, and positional deviation between the contourof the molded article and the pattern.

FIG. 14 and FIG. 15 showed the case in which the molding cavity surface125 of the female die 30b was the recessed shape, but it is apparentthat the present embodiment can be applied to the cases in which themolding cavity surface 125 of the female die 30b is a projectingsurface. In those cases, the stop frame 101 of the sheet clamp 106 iscurved to project out from the female die 30b in a level differencesmaller than the level difference ΔL of the molding cavity surface 125of the female die 30b and in a curvature equal to or smaller than thecurvature of the cavity surface 125.

Further, the line suction groove 104 formed in the female die 30b hasthe same function as that of the many independent suction ports as shownin FIG. 1, and it is a matter, of course, that many suction ports may beformed all over the molding cavity surface instead of the line suctiongroove 104.

Modification 4

Referring to FIG. 16 to FIG. 18, another embodiment of the curved hotplaten used in the apparatus for effecting injection-molded-in foildecoration according to the present invention will be described. Ineither one of the curved hot platens in the previous embodiments, theshape of the heating surface is fixed, and thus, every time the shapesof the molded body to be produced and the sheet clamp are changed, a newcurved hot platen has to be produced in accordance therewith. The curvedhot platen of the present embodiment solves such a problem.

FIG. 16 shows a schematic drawing of the curved hot platen of thepresent embodiment. The curved hot platen 110 is constructed by mountinga plurality of hot platen block units 113 on a flat plate board 112, asshown in the drawing. Plural kinds of hot platen block units 113 areprepared as to the sheet heating bodies such as units having a sheetheating body on only one surface, units having sheet heating bodies ontwo surfaces, units having sheet heating bodies on three surfaces, andunits having no sheet heating body (for example, unit 114), and as tothe thickness and shape, some kinds of units are prepared. A desiredshape of the heating surface can be obtained by suitably combining theseunits and fixing them on the board, for example, by means of screwbolts.

Next described are the details of the board and the hot platen blockunits and a process for mounting the hot platen block units to theboard. As shown in FIG. 17, the board 112 has tapped holes 115 formounting of the hot platen block units and a plurality (3×3=9 in thecase illustrated) of plugs 116 for supplying an electric current toassociated units. Each plug 116 is connected to an unrepresented powersupply by a line 117 extending from the board 112.

As shown in FIG. 18A, a hot platen block unit 113 is formed by attachinga sheet heating body 119 to the surface of a block main body 118 madeof, for example, a ceramic whiteware or a ceramic material, and has aplug socket 120 and bolt-through holes 121 for mounting. The mounting ofthe hot platen block units 113, 114 to the board 112 is effected byscrew bolts 122, as shown in FIG. 17. At that time, a plug 116projecting from the board is inserted into the plug socket 120 of thehot platen block unit 113, 114, which enables an electric current to besupplied to the sheet heating body 119. Among the hot platen blockunits, the unit 114, which is set between another hot platen block unitand the board to be hidden inside the hot platen, has only the plug 116,plug socket 120 and screw holes 121 for passage of the bolts for fixing,but has no sheet heating body, which is thus simply used as a unit forrelay, as shown in FIG. 18B.

The heating surface of the curved hot platen 110 of the presentembodiment is not a perfectly continuous curved surface, but isgenerally of an approximate shape to a desired, curved surface. Further,as shown in FIG. 16, it may have level differences. However, this curvedhot platen 110 can also uniformly heat the decoration sheet 15 deformedand retained by the sheet clamp. Furthermore, the number of the hotplaten block units 114 set on the board 112 may be increased, forexample, to 10×10, thereby dividing the area on the board into finersegments, and many kinds of surface shapes of outermost units areprepared, whereby level differences appearing in the heating surfacebecome small and an arbitrary curved surface can be approximated inhigher precision.

As described above, the curved hot platen 110 of the present embodimenthas a plurality of units 113, 114 combined to each other, and anarbitrary shape of curved surface can be approximated by changing acombination of the units 113, 114. Accordingly, simply preparing acertain number of units 112, 113 whose shapes are different to eachother, the shape of the heating surface can freely be modified bychanging mounting of the units 112, 113, which obviates a need toprepare a new hot platen for every change of the molded body to beproduced.

The present specification has illustrated the present invention mainlywith the examples in which the foil decoration surface of the moldedbody is a curved surface, but it is noted that the present invention isby no means limited to the cases where the entire foil decorationsurface of the molded body is a smoothly continuous, curved surface. Thepresent invention can be applied likewise to such cases that the foildecoration surface of the molded body is a combination of a flat surfaceand a curved surface or a combination of only flat surfaces. In the casethat the foil decoration surface of the molded body contains a flatsurface, the sheet stop frame of the sheet clamp may include a linearportion, and a part or the whole of the heating surface of the hotplaten may be composed of flat surfaces.

In the case that heating is hindered at the portions of the decorationsheet 15 in contact with the sheet stop frames 54, thereby causingdistortion upon stretching because of insufficient softening of theportions, another heater may be added to the stop frames 54 of the sheetclamp 50, which permits the decoration sheet 15 to be heated moreuniformly.

Heating of the decoration sheet 15 by the hot platen may rely on amethod for directly heating the decoration sheet 15 in contact with thehot platen mainly by heat conduction (a contact heating method) or on amethod for heating the decoration sheet 15 mainly by infrared radiationfrom the curved hot platen (heating surface) as keeping the patternportion of the decoration sheet 15 not in contact with the heatingsurface (a non-contact heating method).

Embodied means of the contact heating method is, for example, a methodarranged in such a manner that the surface shape of the hot platen 60 ismade to be the same as the shape of the decoration sheet 15 deformed andretained. In this case, suction ports, which are similar to thosedisclosed in Japanese Laid-open Patent Application No. 59-31130, areformed in the surface of the hot platen 60, and the decoration sheet 15is heated as kept in close fit to the surface of the hot platen 60 byvacuum suction. Embodied means of the non-contact heating method is, forexample, a method of radiation heat arranged in such a manner that thesurface shape of the hot platen is made to be the same as the shape ofthe deformed and retained sheet. In this case, a peripheral wall forretaining the sheet having suction ports in the surface thereof, whichis disclosed for example in Japanese Laid-open Patent Application No.5-301250, is formed in the periphery thereof, and the sheet is fixed ata distance corresponding to the height of the peripheral wall from thesurface of the hot platen by the periphery wall, to be heated apart.

The decoration sheet 15 includes a substrate sheet 15a and a decorativelayer 15b laminated thereon, and may be either the bonded and layeredfilm. A final product is obtained as the substrate sheet 15a and thedecorative layer 15b are integrated in fit with the molded article, orthe transfer sheet 15b is left on the molded article side and thesubstrate sheet 15a is peeled off after the decoration sheet 15 and themolded article Q are once integrated with each other. The substratesheet 15a applicable may be a thermoplastic resin such as a polyvinylchloride, an acrylic resin, a polystyrene, an ABS resin, apolycarbonate, a polyester, a polypropylene, etc. The thickness of thesubstrate sheet 15a is usually in the range of from about 20 to about500 μm. The decorative layer 15b may be a print pattern layer, a coloredor transparent coating layer, or a metal thin film, etc.

The female die 30 and the male die 40 used in the apparatus foreffecting injection-molded-in foil decoration of the present inventionmay have fundamentally the same structure as those in the conventionalapparatus, and an uneven pattern or the like may be formed on themolding surfaces of the female die 30 and the male die 40 (whereby anuneven pattern is formed on the molded body accordingly). A material forthe female die 30 and male die 40 may be a metal such as iron or aceramic material. A suction path is preferably formed inside the femaledie 30 in order to draw the decoration sheet 15 softened by heating, anend of which is connected to a pressure reducing device such as a vacuumpump and the other end of which opens on the molding cavity surface 31a.Further, in the case that the female die 30 is made of a porous ceramicor a porous metal, the porous structure itself may be used as thesuction path and suction port.

The injection molding according to the present invention includes thereactive injection molding (so-called RIM molding) for injecting anuncured solution of a curing type resin to be cured by a chemicalreaction in addition to the method for injecting a heat-meltedthermoplastic resin. In the case of the reactive injection molding, aresin "solution" which is not heat-melted is used. Accordingly, the"molten resin" in the present specification includes a solution of theabove resin in addition to the resin in a heat-melted state.

By the process and apparatus for effecting injection-molded-in foildecoration of the present invention, the decoration sheet 15 canuniformly be heated and softened without irregularity. Further, thedeformation amount can be reduced in premolding of the decoration sheet15 heated and softened into the molding cavity surface 31a of the femaledie 30, which decreases distortion, appearance of wrinkles or breakageof the decoration sheet 15, positional deviation between the decorativelayer 15b and the contour of the molded article, and distortion of thedecorative layer 15b. Accordingly, the foil decoration can be effectedin high quality to the molded article having large level differences orlarge curvature of the surface.

Second Embodiment

FIG. 19 is a schematic drawing to show the second embodiment of thepresent invention. In the drawing, hatched portions show cut surfaces.The apparatus of the present embodiment is provided with a female die230 and a male die 240 arranged to be opposed to the female die 230similarly as in the conventional example. Further, it is provided with adecoration sheet 215 unwound from a decoration sheet feed roll 216, asheet clamp 250 having functions to support the decoration sheet 215 andalso to house and retain a flexible sheet heating body 260, and theflexible sheet heating body 260 is used for generating heat for heatingand softening the decoration sheet 215.

Formed in the female die 230 is a cavity 231 having a molding cavitysurface 231a corresponding to the contour of the molded body to bemolded, and a plurality of suction ports 232 opening on the cavitysurface 231a are formed inside the female die 230. The suction ports 232are connected to an unrepresented vacuum pump through a suction tube233. The male die 240 is fixed to a stationary platen 244 and the femaledie 230 is connected to a hydraulic cylinder 235 through a moving platen234, whereby the female die 230 can be movable relative to the male die240. Further, as in the conventional case, the male die 240 has a core242, which is to be inserted into the molding cavity 231 of the femaledie, and a pouring port 247 of a molten-resin-injecting unit is formedtherein.

The sheet clamp 250 is a frame member made of, for example, stainlesssteel, which is fixed to slide rods 257 attached to the female die 230and which is driven by an unrepresented driving mechanism so as to moveaway from the cavity surface 231a toward the male die 240. As shown inFIG. 20, the sheet clamp 250 has a slit 253 for the flexible sheetheating body 260 to be inserted into and guide grooves 254 for guidingrollers 265 fixed to the both side edges of the sheet heating body 260.This slit 253 opens on the inserting side of the sheet heating body 260as illustrated (upward in FIG. 20), and is a cavity expanding in thefeeding direction of the sheet heating body in the sheet clamp 250.Further, the slit 253 may be arranged either to or not to penetrateupper and lower stop frames 251a, 251b of the sheet clamp 250. Curvedright and left stop frames 252a, 252b have a level difference smallerthan that of the cavity surface 231a of the molding cavity 231, and acurvature equal to or smaller than that of the cavity surface 231a ofthe cavity 231, and retain the decoration sheet 215 in such a state thatthe sheet 215 is pushed into the cavity 231.

The flexible sheet heating body 260 is obtained by adhering to a thinelastic steel plate, a sheet heater, such as one formed in such a mannerthat a heating element constituted for example by spirally winding afine resistance wire around a glass fiber cord is arranged in a sheetform in accordance with a predetermined pattern, the sheet is setbetween two thin silicone rubber sheets reinforced with glass fibers,and the resultant is then vulcanized, or a sheet heater formed in such amanner that a coating layer of resistor is formed on a heat resistantresin substrate and the surface is covered by an electrically insulatinglayer. The heating body has the thickness of about from 0.5 to 2 mm andis arranged to obtain a uniform temperature distribution with supply ofan electric current. Further, the flexible sheet heating body 260 may becomposed of a plurality of rectangular hot platens connected by hinges.Shafts 264 are fixed to the both side edges of the flexible sheetheating body 260 throughout a predetermined length from the lower endportion by means of screwing, and rollers 265 are attached as rotatableeach to the tips of the shafts 264. The rollers 265 are guided in guidegrooves 276 of sheet heating body guide rails 270, as shown in FIG. 21.Further, guide members which are guided as not rotating but sliding inthe guide grooves may be used in place of the rollers 265.

Next described is a process for effecting foil decoration at the sametime as injection molding, using the apparatus of the presentembodiment.

As shown in FIG. 19, the decoration sheet 215 is drawn out from the feedroll 216 by the pair of lead-on rollers 217, 217, and is guided by theguide roller 218, thereby running in front of the female die 230. Theend of the decoration sheet is pulled in toward the arrow direction byan unrepresented means so that the decoration sheet 215 may be kept notloosened. Desired patterns are printed at a predetermined pitch on thedecoration sheet 215. In the case that the sheet is either a reverseprinting bonded and layered sheet or a transfer sheet, the printedsurface is set on the opposite side to the female die 230; in the caseof a normal printing bonded and layered sheet, the printed surface isset on the female die 230 side. Further, positioning marks 214 (forexample, register marks, cross marks, rectangles, stripes, etc.) areprinted at a predetermined pitch or in an endless manner (as stripepatterns) on the decoration sheet 215 together with the patterns.

First, the decoration sheet 215 is unwound by a length of one shot fromthe feed roll 216 by the lead-on rollers 217, 217 in such a state thatthe sheet clamp 250 is placed apart from the female die 230 by the sliderods 257.

This one-shot unwinding and positioning of a pattern relative to thefemale die 230 is completed by stopping the drive of the sheet when aposition sensor 219 such as a phototube detects the mark 214 on thesheet. In order to enable positioning in the longitudinal and lateraldirections of the decoration sheet 215, it is ordinary practice to setvertical and horizontal pairs of position sensors, for example. Further,in the case that the patterns of the decoration sheet 230 are asingle-colored pattern over the entire surface, which does not requirepositioning, this positioning step and printing of the positioning markson the decoration sheet can be omitted.

Next, the slide rods 257 are drawn back toward the female die 230 towithdraw the sheet clamp 250 toward the female die 230, and thedecoration sheet 215 is fixedly retained between the upper and lowerstop frames 251a, 251b of the sheet clamp 250 and the parting surface ofthe female die 230. At the same time, the decoration sheet 215 is pushedinto the molding cavity 231 by the right and left stop frames 252a, 252bof the sheet clamp 250, thereby being deformed into the shape having alevel difference smaller than that of the cavity surface 231a of thecavity 231 and a curvature equal to or smaller than that of the cavitysurface. Then, the sheet clamp 250 is incorporated with the female die230 to constitute a part thereof.

The shape, the curvature, etc. of the right and left stop frames 252a,252b of the sheet clamp 250 are so designed that no wrinkle or nobreakage appears in the deformed decoration sheet 215 projecting intothe cavity 231 when pushed thereby, similarly as in the firstembodiment. Further, a preferred embodiment capable of particularlyreducing wrinkles on the decoration sheet 215 may be arranged in such amanner that the upper and lower stop frames 251a, 251b of the sheetclamp 250 are formed in a flat plate shape with no curvature; the widthWc of the sheet clamp frame body 250 is set to be wider than the widthWs of the decoration sheet 215; the both side ends of the decorationsheet 215 are in contact with the right and left stop frames 252a, 252bover about a half of the overall width thereof Wf; and the decorationsheet 215 is not out from the both sides of the stop frames 252a, 252b(Wc-2Wf<Ws<Wc). This arrangement makes the decoration sheet 215 curvedonly in one direction (in the vertical direction in FIG. 20), whichhardly forms a wrinkle on the decoration sheet 215. In this case, thecavity surface 231a of the molding cavity 231 may have a shape curved intwo or more directions (for example, in the vertical and horizontaldirections), whereby the same effects can be achieved.

Next, the female die 230 is advanced toward the male die 240 by drivingthe hydraulic cylinder 235, and it is stopped at a position where thetop end of the sheet clamp 250 is located right under the bottom ends ofthe guide rails 270 for the sheet heating body 260, as shown in FIG. 22.Then, the guide rails 270 for the sheet heating body 260 are lowered tobring the bottom ends of the guide rails 270 of the sheet heating body260 and the top end of the sheet clamp 250 into contact with each otheras shown in FIG. 23, thereby continuously joining the guide grooves 276of the guide rails 270 of the sheet heating body 260 with the guidegrooves 254 of the sheet clamp 250.

As shown in FIG. 21, housings 271 for fixing and transferring the guiderails are fixed to the molding machine and the guide rails 270 for thesheet heating body 260 are retained by stop fittings 277 so as to bemovable up and down relative to the housings 271. The guide rails 270move downward when a chain 272 set in the housing 271 is driven by anunrepresented power source such as an electric motor. When the chain 272is driven, pinions 273 attached to the housing 271 rotate. The pinions273 mesh with racks 275 formed on the side surfaces of the guide rails270, and the guide rails 270 descend with rotation of the pinions 273.

Next, a pair of lead-on rollers 262, 262 are driven to unwind a windingand unwinding roller 261 for the sheet heating body 260 and to feed theflexible sheet heating body 260 out. The flexible sheet heating body 260thus fed out is inserted into the slit 253 of the sheet clamp 250 whilethe rollers 265 at the both side edges are guided by the guide grooves254, thereby changing into a curved shape along the shape of the sheetclamp 250. Since the bottom ends of the guide rails 270 for the sheetheating body and the top end of the sheet clamp 250 are in contact witheach other as described above, the flexible sheet heating body 261 issmoothly introduced into the sheet clamp 250. The feeding driving of thesheet heating body 260 is stopped when the flexible sheet heating body260 comes to be set over the entire surface of the sheet clamp 250. Inthis case, a necessary function is to cover the entire aperture enclosedby the upper and lower and right and left stop frames 251a, 251b, 252a,252b in the center of the sheet clamp 250 with the sheet heating body260. It is not necessarily required that the sheet heating body 260penetrate the lower stop frame 251b. In this state, the flexible sheetheating body 260 inserted and retained in the slit 253 of the sheetclamp 250 becomes a curved hot platen having the same or substantiallythe same shape as that of the decoration sheet 215 pushed and deformedby the sheet clamp 250.

The distance ΔL between the decoration sheet 215 and the sheet heatingbody 260 is kept constant as shown in FIG. 24. An electric current issupplied to the flexible sheet heating body 260 in this state, therebyheating and softening the entire surface of the decoration sheet 215uniformly. After completion of heating and softening of the decorationsheet 215, the inside of the molding cavity 231 of the female die 230 isevacuated through the suction ports 232 by operating the unrepresentedvacuum pump, whereby the softened decoration sheet 215 pushed andretained by the sheet clamp 250 is drawn into close fit to the moldingcavity surface 231a.

At this time, the flexible sheet heating body 260 is wound back by thewinding and unwinding roller 261 for the sheet heating body, whereby theheating body 260 is withdrawn out of the slit 253 of the sheet clamp 250upward, and further, the chain 272 in the housing 271 is driven in thereverse direction. By this operation, the pinions 273 are driven in thereverse direction and an action of the racks 275 meshed with the pinions273 retracts the guide rails 270 for the sheet heating body 260 to anupward position where they do not hinder clamping of the female and maledies 230, 240. Thus, the flexible sheet heating body 260 and the guiderails 270, which could obstruct coupling of the female and male dies230, 240 and injection of a molten resin, both are withdrawn from thefemale and male dies 230, 240.

According to the premolding step of the present invention, thedecoration sheet 215 is preliminarily made to be projected and deformedin the molding cavity 231 of the female die 230 by the sheet clamp 250,the decoration sheet 215 is heated and softened in that state, andthereafter it is shaped into fit to the molding cavity surface 231a.This decreases a deformation amount (stretching amount) of the softeneddecoration sheet 215 and a stretching speed when the sheet is drawn intoclose fit to the cavity surface 231a, which can reduce distortion,wrinkles, and breakage of the decoration sheet 215 and positionaldeviation between the pattern and the contour of the molded article.

Next, the female die 230, in which the sheet clamp 250 is incorporatedas a constituent, is further advanced by the hydraulic cylinder 235, sothat the female die 230 comes to couple with the male die 240 to effectdie clamping, as shown in FIG. 25, and thereafter the molten resin ispoured to fill in the cavity 231 through the pouring port 247 of theinjecting unit formed in the male die 240, thereby effecting injectionmolding. The molten resin is poured to fill through the aperture of thesheet clamp 250. At this time, the slit 253 exposed to the aperture ofthe sheet clamp frame body 250 is closed by the core 242 of the male die240, and, therefore, no molten resin goes into the slit 253 or the guidegrooves 254 of the sheet clamp 250. After the injected resin is cooledand solidified in this state, the decoration sheet 215 in the female die230 becomes adhering to the injected resin as incorporated therewith.

The injected resin may be a resin solution which is cured by a chemicalreaction, such as a polyurethane using an isocyanate as a curing agentor an unsaturated polyester using an isocyanate, an organic sulfonate orthe like as a curing agent in addition to a fluidized thermoplasticresin as heat-melted, such as a polyvinyl chloride, a polystyrene, anABS resin, an acrylic resin, or a polycarbonate.

Next, as shown in FIG. 26, the female and male dies 230, 240 are openedto release a molded body with foil decoration Q from the dies. Here, ifthe decoration sheet 215 is a bonded and layered film (laminate film),the foil decoration is already performed as it is, and all the layers ofthe decoration sheet 215 are adhered to be integrated onto the surfaceof the molded body Q to form a decorative layer (FIG. 8A). On the otherhand, in the case that the decoration sheet 215 is a transfer film, onlya base sheet 215a of the decoration sheet 215 integrated on the surfaceof the molded body Q is peeled off in a later step so that a transferlayer 215b including a pattern layer, etc. may be left on the moldedbody Q side to form a decorative layer, thereby completing the foildecoration (FIG. 8B).

Immediately after the die opening, the molded body Q often remainsadhering to the surface of the cavity 231a of the female die 230 or thesurface of the male die 240. In order to release the molded body Q fromthe dies 230, 240, thereby certainly bringing it into the state of FIG.26, a known ejector is used to facilitate release from the dies 230,240, though it is not shown. As an example of the ejector, a slide rodmay be set as capable of being projected and withdrawn in the male die240 or the female die 230, which is projected after the die opening torelease the molded body Q from the die. In the steps except for thereleasing step, the slide rod is kept as withdrawn to such a positionthat the top surface thereof is located at the same level as the surfaceof the die.

According to the present embodiment, the flexible sheet heating body 260is inserted into the sheet clamp 250 to be deformed into its shape, and,therefore, there is no need to prepare a hot platen for heating andsoftening the decoration sheet 215, separately from the sheet clamp 250.In other words, curved hot platens of various shapes can be constitutedautomatically by one type of the flexible sheet heating body 260 only byreplacing the sheet clamp 250, which can obviate a need to produce a newhot platen for every shape of molded article Q. Further, since the sheetclamp 250 also serves as a hot platen, the surface of the hot platenchanges with good precision into the same shape as the decoration sheet215 preliminarily deformed, and the decoration sheet 215 can be heateduniformly at an equal distance. The weight of the hot platen becomeslighter than a hot platen made of a rigid body as employed in theconventional case, whereby the driving mechanism becomes simpler.

Modification 1

Another example of modification of the apparatus for effecting foildecoration at the same time as injection molding according to thepresent invention is described referring to FIG. 27 and FIG. 28.

The present embodiment employs a sheet clamp 280 having only a functionto fix and retain the decoration sheet 215 on the female die 230, and aframe body 290 for housing a sheet heating body, independent thereof.The two frame bodies 280, 290 are independently driven by separate sliderods formed in the female die 230. Namely, the sheet clamp frame body280 is driven by slide rods 282 and the other frame body 290 is drivenby slide rods 292 arranged as coaxial with the slide rods 282.

The sheet clamp 280 is a dedicated frame body for fixing and retainingthe decoration sheet 215 on the female die 230, which has a shapesimilar to the sheet clamp 250 as shown in FIG. 20, and which has anaperture in the center, but has neither slit 253 nor guide grooves 254.On the other hand, the frame body 290 for housing the sheet heating bodyhouses the flexible sheet heating body 260, and heating the decorationsheet 215 pushed by the sheet clamp 280 and thus stereoscopicallydeformed, as keeping it at an equal distance. It has substantially thesame shape as the sheet clamp 280, and has a slit 290a for the flexiblesheet heating body 260 to be inserted therein and guide grooves 290b forguiding guide rollers 265 provided at the both side edges of theflexible sheet heating body 260, as the sheet clamp 250 shown in FIG. 20had.

The sheet clamp 280 remains still as keeping the decoration sheet 215 onthe female die 230 until the molded article Q is taken out. On the otherhand, after the frame body 290 for housing the sheet heating body housesthe flexible sheet heating body 260 in the slit 290a, it is movedforward or backward through drive of the slide rods 292 to change adistance ΔL' between the two frames 280, 290, thereby changing thedistance between the sheet heating body 260 and the decoration sheet215, as shown in FIG. 27, which enables heating at an optimum distancefor every one of various shapes of the decoration sheet 215 and moldedarticle Q. Namely, supposing the thickness of the sheet clamp 280 is ΔL"and the distance between the sheet clamp 280 and the frame body 290 forhousing the sheet heating body is ΔL', the distance ΔL between thedecoration sheet 215 and the hot platen is given as ΔL=ΔL'+ΔL".

At the point of completion of the premolding of the decoration sheet 215to the cavity surface 231a of the female die 230, the slide rods 292 fordriving the frame body 290 for housing the sheet heating body are movedto bring the sheet clamp 280 into contact with the frame body 290 forhousing the sheet heating body to be coupled therewith, as shown in FIG.28, thereby determining the volume of the molding cavity 231 and sealingthe sheet clamp 280 and the frame body 290 for housing the sheet heatingbody. Then, the female and male dies 230, 240 are coupled with eachother to clamp the dies by the hydraulic cylinder 235, and injection ofthe molten resin is carried out.

According to the present embodiment, the distance L between thedecoration sheet 215 and the sheet heating body 260 can be set to adesired length, so that optimum heating conditions can be advantageouslyset for each of various decoration sheets 215 and each of variousmolding shapes.

The decoration sheet 215 has a substrate sheet 215a and a decorativelayer 215b laminated thereon. A final product is obtained as thesubstrate sheet 215a and the decorative layer 215b are integrated in fitwith the molded article, or the transfer sheet 215b is left on themolded article side and the substrate sheet 215a is peeled off after thedecoration sheet 215 and the molded article Q are once integrated witheach other. The substrate sheet 215a applicable may be a thermoplasticresin such as a polyvinyl chloride, an acrylic resin, a polystyrene, anABS resin, a polycarbonate, a polyester, a polypropylene, etc. Thethickness of the substrate sheet 215a is usually in the range of fromabout 20 to about 500 μm. The decorative layer 215b may be a printpattern layer, a colored or transparent coating layer, or a metal thinfilm, etc.

The female die 230 and the male die 240 used in the apparatus foreffecting injection-molded-in foil decoration of the present inventionmay have fundamentally the same structure as those in the conventionalapparatus, and an uneven pattern or the like may be formed on themolding surfaces of the female die 230 and the male die 240 (whereby anuneven pattern is formed on the molded body accordingly). A material forthe female die 230 and male die 240 may be a metal such as iron or aceramic material. A suction path is preferably formed inside the femaledie 230 in order to draw the decoration sheet 215 softened by heating,an end of which is connected to a pressure reducing device such as avacuum pump and the other end of which opens on the molding cavitysurface 231a. Further, if the female die 230 is made of a porous ceramicor a porous metal, the porous structure itself may be used as thesuction path and suction port.

The decoration sheet 215 may be supplied in a necessary amount from acontinuous band film wound in the coil form or may be supplied as batchsheet films preliminarily cut into in a predetermined size.

The injection molding according to the present invention includes thereactive injection molding (so-called RIM molding), for injecting anuncured solution of a curing type resin to be cured by a chemicalreaction, in addition to the method for injecting a heat-meltedthermoplastic resin. In the case of the reactive injection molding, aresin "solution" which is not heat-melted is used. Accordingly, the"molten resin" in the present specification includes a solution of theabove resin in addition to the resin in a heat-melted state.

By the process and apparatus for effecting injection-molded-in foildecoration of the present invention, the decoration sheet 215 canuniformly be heated and softened without irregularity. Further, thedeformation amount can be reduced in premolding of the decoration sheet215 heated and softened into the molding cavity surface 231a of thefemale die 230, which decreases distortion, appearance of wrinkles andbreakage of the decoration sheet 215, positional deviation between thedecorative layer 215b and the contour of the molded article, anddistortion of the decorative layer 215b. Accordingly, the foildecoration can be effected in high quality to the molded article havinglarge level differences or large curvature of the surface. Further, thesurface shape of the hot platen 260 becomes the same with good precisionas the decoration sheet 215 preliminarily deformed, and the decorationsheet 215 can be heated uniformly at an equal distance. The hot platenbecomes lighter in weight than a hot platen made of a rigid body asemployed in the conventional case, whereby the driving mechanism becomessimpler.

Third Embodiment

Below described is the third embodiment of the present invention,referring to drawings. FIG. 29 to FIG. 43B are drawings to show theprocess and apparatus for effecting injection-molded-in foil decorationaccording to the present invention.

First, the apparatus for effecting injection-molded-in foil decorationis described with reference to FIG. 29 to FIG. 34. As shown in FIG. 29,the apparatus for effecting injection-molded-in foil decoration isprovided with a cavity 331 having a cavity surface 331a, a female die330 having suction ports 322 opening on the cavity surface 331a, and amale die 340 arranged to be opposed to the female die 330 and having acore 342 and a resin pouring port 327. The cavity surface 331a of thefemale die 330 is of a semicylindrical shape with the center axis on thex axis. Further, as shown in FIG. 29 and FIG. 30, a sheet clamp 350 isformed between the female die 330 and the male die 340, as retaining adecoration sheet 315 in cooperation with a cavity periphery 331b of thefemale die 330.

The sheet clamp 350 has right and left stop frames 352a, 352b, and topand bottom stop frames 351a and 351b, and an aperture 380 as enclosed bythese stop frames 352a, 352b, 351a, 351b is formed. Further, asemicircular curved projection 350a with the center axis on the x axisis formed so as to project in each of the right and left stop frames352a, 352b of the sheet clamp 350. Furthermore, a slit 353 is formed inthe sheet clamp 350 in order that a flexible sheet heating body 360described below is inserted therein so as to be curved substantially inthe same shape as that of the decoration sheet 315 retained on thefemale die 330. This slit 353 opens on the insertion side of the sheetheating body 360 (upward in FIG. 29), as shown in the drawing, andexpands in the feed direction of the sheet heating body 360 (downward inFIG. 29). Further, guide grooves 354 are formed along the both sideedges of the sheet clamp 350. This slit 353 may or may not penetrate thebottom stop frame 351b of the sheet clamp 350 as long as the sheetheating body 360 can cover the aperture 380. Furthermore, the sheetclamp 350 is connected to the female die 330 through slide rods 357, andthe sheet clamp 350 is arranged to move toward or away from the femaledie 330 through the slide rods 357, which slide as penetrating theexternal parting surface of the cavity 331 of the female die 330.

The surface of the cavity periphery of the female die 330 (which isgenerally called as a parting surface) has top and bottom partingsurfaces 331c, 331c, which are to match (fit) with the top and bottomstop frames 351a, 351b located at the top and the bottom of the sheetclamp 350 and opposed thereto, and right and left parting surfaces 331b,331b, which are to match the curved projections 350a, 350a located rightand left of the sheet clamp 350 and opposed thereto. Each of the rightand left parting surfaces 331b, 331b is provided with a semicircular,curved recess 330a with the center axis on the x axis, corresponding tothe projection 350a of the sheet clamp 350, and a pair of sheet guidegrooves 382 are formed in the surfaces of the curved recess 330a. Thedepth of the curved recess 330a of the female die 330 from the top andbottom parting surfaces 331c is determined to be substantially the sameas the height of the projections 350a of the sheet clamp 350, but it issmaller than the depth of the cavity surface 331a. Further, thecurvature of the recess 330a of the female die 330 is smaller than thatof the cavity surface 331a. Furthermore, in the top, bottom, right andleft parting surfaces of the female die 330, the periphery close to thecavity 331 is called as a cavity periphery. A ring groove 392a (see FIG.37) is formed here, and an O ring 392 is fit in the ring groove 392a. Asuction tube 333 is provided in communication with suction ports 322 inthe female die 330.

Further, a decoration sheet feed roll 316 is arranged above the femaledie 330 in order to successively supply an elongate band-shapeddecoration sheet 315, and the decoration sheet 315 from the decorationsheet feed roll 316 is supplied toward the cavity 331 of the female die330 through lead-on rollers 317, 317. Furthermore, the decoration sheet315, supplied to the cavity 331 of the female die 330 through thelead-on rollers 317, 317, is so arranged that the both side edges arepinched by sheet pinching means 388.

The sheet pinching means 388 is fixed to wires 387 unwound from a sheetpinching means feed roll 390, and the wires 387 are unwound by rotatingthe sheet pinching means feed roll 390 by an electric motor 391 to drawthe sheet pinching means 388. A sheet pinching means 388 has a pair ofpinching members 388a, 388a for pinching the either side edge of thedecoration sheet 315 and a roller (guide member) 389 connected to thepair of pinching members 388a, 388a, among which the roller 389 isarranged to go into a sheet guide rail 381 and then go into the sheetguide groove 382 of the female die 330.

Then the decoration sheet 315 sent downward from the lead-on rollers 317is pulled downward as held by a pulling chuck 386 after the tip endthereof is detected by a position sensor 383. This pulling chuck 386moves in the sheet feed direction (in the vertical (Z) direction in FIG.30) by means of a cylinder mechanism or the like, which is not shown.

Further, a cutter guide rail 384 is arranged in the horizontal directionabove the female die 330, and a sheet cutter 385 is arranged so to runalong the cutter guide rail 384.

Furthermore, the sheet heating body 360 is arranged to be inserted intothe slit 353 of the sheet clamp 350, and the both side edges of thesheet heating body 360 are pinched by clamp members 364. Rollers 365 areconnected to the clamp members 364. The rollers 365 are inserted intothe grooves 376 of the guide rails 370 set above the sheet clamp 350,and then the rollers 365 enter the guide grooves 354 in the sheet clamp350 from the guide rails 370.

Next, the sheet pinching means 388 is described in detail with referenceto FIG. 35 to FIG. 38. As shown in FIG. 35 to FIG. 38, a sheet pinchingmeans 388 has a pair of sheet pinching members 388a, 388a connected toeach other as rockable about a pivot 387, and a return spring 396between the pair of pinching members 388a, 388a, and the roller 389 isconnected to one pinching member 388a. On the other hand, a projection395 is formed at the end of the other pinching member 388a.

Incidentally, the female die 330 described above is fixed to a movingplaten 334, and the female die 330 fixed to the moving platen 334 isarranged to move toward the male die 340, which is fixed to a stationaryplaten 344. Further, the decoration sheet feed roll 316 and the sheetpinching means feed roll 390 are fixed to the moving platen 334, thoughnot shown, and thus, they are arranged to move together with the femaledie 330. Also, the guide rails 370 are arranged to move together withthe sheet clamp 350.

Next described is the operation of the present invention in the aboveconstitution.

FIG. 30 shows a state of starting a next molding cycle after finishing aprevious molding cycle. In FIG. 30, the female die 330 and the male die340 (not shown in FIG. 30) are separate from each other, and the sheetclamp 350 is also separated from the female die 330 by projection of theslide rods 357. The flexible sheet heating body 360 is waiting above thesheet clamp 350. Further, the decoration sheet 315 is unwound from thedecoration sheet feed roll 316 so that the tip end of the decorationsheet 315 may be located at a position where it is fed out from thelead-on rollers 317. Furthermore, the tip end of the decoration sheet315 is pinched by the pulling chuck 386.

Further, as shown in FIG. 30, a plurality of sheet pinching means 388are connected at predetermined intervals to the wires 387 unwound fromthe sheet pinching means feed roll 390, and the width between the wires338 is slightly wider than that of the decoration sheet 315. Also, thepinching members 388a, 388a of each sheet pinching means 388 are waitingin an open state above the female die 330.

Next, a new molding cycle is started from such a state. Namely, as shownin FIG. 30, the elongate band-shaped decoration sheet 315 is unwoundfrom the decoration sheet feed roll 316 and the tip end of thedecoration sheet 315 is detected by the position sensor 383. Then thetip end of the decoration sheet 315 is pulled downward (in the zdirection) by the pulling chuck 386, and the tip end of the decorationsheet 315 reaches a position lower than the lowest out of the sheetpinching means 388. At that time, the both side edges of the decorationsheet pass between the pinching members 388a, 388a which are kept open.

Next, the paired pinching members 388a, 388a of each sheet pinchingmeans 388 are closed to pinch the either side edge of the decorationsheet 315 between the paired pinching members 388a, 388a, as shown inFIG. 31.

In this case, each sheet pinching means 388 operates as follows: theprojection 395 at the tip of the one pinching member 388a is firstpushed by a driving means such as a solenoid or a hydraulic cylinder toopen the pair of pinching members 388a, 388a, as shown in FIG. 38. Next,the both side edges of the decoration sheet 315 are inserted between thepair of pinching members 388a, 388a, and then the driving means isreleased to close the pair of pinching members 388a, 388a by the returnspring 396.

At the same time, as shown in FIG. 31, the sheet heating body 360 islowered and the rollers 365 connected to the clamp members 364 forpinching the both side edges of the sheet heating body 360 go into theguide grooves 354 of the sheet clamp 350 from the grooves 376 of theguide rails 370. When the rollers 365 enter the guide grooves 354 inthis manner, the sheet heating body 360 comes into the slit of the sheetclamp 350.

Then, as shown in FIG. 32, the tip end of the decoration sheet 315 isfurther pulled down by the pulling chuck 386. In this case, the roller389 of each sheet pinching means 388 enters the sheet guide groove 382of the female die 330, whereby the sheet decoration sheet 315 isbecoming curved along the surfaces of the grooves 330a of the female die330 accordingly.

As shown in FIG. 29 to FIG. 33, the shape of the recess 330a of thefemale die 330 is similar to the shape of the cavity 331 of the femaledie 330, but the depth of the recess 330a from the top and bottomparting surfaces 331c, 331c is smaller than the depth of the cavity 331.Further, the curvature is arranged to be the same as or smaller thanthat of the cavity surface 331a. Therefore, the decoration sheet 315,which is curved along the surfaces of the recess 330a of the female die330, is in such a state that it is substantially along the cavitysurface 331a. Thus, the cavity 331 of the female die 330 is covered bythe decoration sheet 315. At that time, the depth and the radius ofcurvature of the recess 330a are preferably so determined that the depthis as deep as possible and the curvature is substantially at the samelevel as that of the cavity surface 331a within the range enough for thedecoration sheet 315 to be deformed with neither wrinkle nor breakagewhen it is curved without heating and softening.

At the same time, as shown in FIG. 32, the rollers 365 connected to theclamp members 364 for pinching the sheet heating body 360 go into theguide grooves 354 of the sheet clamp 350. In this case, the sheetheating body 360 is curved substantially in the same shape as theprojections 350a of the sheet clamp 350, that is, substantially in thesame shape as the decoration sheet 315 on the surfaces of the recess330a of the female die 330.

Next, as shown in FIG. 33, the position sensor 383 detects that thedecoration sheet 315 reaches the predetermined position and the pullingoperation by the pulling chuck 386 stops. Thereafter, the pulling chuck386 is withdrawn from the decoration sheet 315 and instead thereof, thetip end of the decoration sheet 315 is clamped by fixing chucks 393. Thepulling chuck 386 away from the decoration sheet 315 is raisedthereafter to reach the standby position above the female die 330.

Then, as shown in FIG. 34 and FIG. 39, the slide rods 357 are withdrawntoward the female die 330 (in the y direction). After the sheet clamp350 moves to the female die 330 thereby, it comes to fit into closecontact with the female die 330, whereby the decoration sheet 315 isretained between the sheet clamp 350 and the female die 330. In thiscase, the sheet clamp 350 is in close contact with the O ring 392 of thefemale die 330 with the decoration sheet 315 inbetween to seal thecavity 331 of the female die 330.

During this period, the pair of pinching members 388a, 388a of the sheetpinching means 388 remain pinching the decoration sheet 315 as shown inFIG. 36. Further, the sheet clamp 350 is in close contact with thefemale die 330 and the decoration sheet 315 is retained between thefemale die 330 and the sheet clamp 350, whereby the sheet heating body360 in the sheet clamp 350 can be located with a certain gap relative tothe decoration sheet 315.

Next, as shown in FIG. 37, the driving means drives the projection 395to open the pair of pinching members 388a, 388a of the sheet pinchingmeans 388, thereby releasing the decoration sheet 315 from the sheetpinching means 388. Then, the wires 387 are wound by the sheet pinchingmeans feed roll 390 to raise the sheet pinching means 388 along thesheet guide grooves 382 of the female die 330 and the sheet guide rails381, and wait at the standby position above the female die 330.Accordingly, the sheet pinching means 388 is withdrawn in this mannerfrom the sheet guide grooves 382 of the female die 330 (see FIG. 38).

Thereafter, the sheet cutter 385 runs in the widthwise direction of thedecoration sheet 315 along the cutter guide rail 384, whereby thedecoration sheet 315 is cut by the sheet cutter 385. The running of thesheet cutter 385 is realized, for example, by a rack and pinionmechanism or an air cylinder. The reason why the decoration sheet 315 iscut as above is to prevent deformation or silica appearing in premoldingof the decoration sheet 315 and injection molding from affecting ordeforming the decoration sheet 315 used for the next molding.

Then, as shown in FIG. 40, the decoration sheet 315 is returned to thestandby position by winding the sheet feed roll 316 and the tip of thedecoration sheet 315 is pinched by the pulling chuck 386 (see FIG. 30).

During the above operation, the decoration sheet 315 is uniformly heatedand softened by the sheet heating body 360 in the sheet clamp 350. Thisheating is performed mainly by radiation heat in a non-contact manner.After completion of the heating to soften the decoration sheet 315, thesheet heating body 360 is pulled up from inside the sheet clamp 350, asshown in FIG. 41. Then the sheet heating body 360 waits above the sheetclamp 350.

Next, suction is effected from the suction ports 332 of the cavitysurface 331a through the suction tube 333 of the female die 330 by theunrepresented vacuum pump, and the softened decoration sheet 315 comesto adhere to the cavity surface 331a to effect premolding.

Next, as shown in FIG. 42, the female die 330 fixed to the moving platen334 moves together with the sheet clamp 350 toward the male die 340fixed to the stationary platen 344, whereby the female die 330, sheetclamp 350 and male die 340 are coupled to achieve die clamping. At thattime, the slit 353 and the guide grooves 354 of the sheet clamp 350 aresealed by the core 342 of the male die 340. Next, an injecting resin ispoured through the resin pouring port 327 of the male die 340 into thecavity 331 between the female die 330 and the male die 340 through theaperture 380 of the sheet clamp 350, thereby obtaining the moldedarticle Q (see FIG. 7) of the resin thus injected. In this case, apattern or letters are deposited on the surface of the article Q at thesame time as molding thereof.

After that, the slide rods 357 project out to separate the female die330 from the sheet clamp 350 and the male die 340, thereby effecting dieopening among the female die 330, the sheet clamp 350, and male die 340.After the die opening among the female die 330, sheet clamp 350, andmale die 340 in this manner, the molded article Q is taken out from thefemale die 330. In this case, the molded article Q can be easily takenout by pushing the molded article Q with a taking-out rod (not shown)from the female die 330 side or the sheet clamp 350 side.

The flexible sheet heating body 360 is obtained by adhering to a thinelastic steel plate, a sheet heater, such as one formed in such a mannerthat a heating element constituted for example by spirally winding afine resistance wire around a glass fiber cord is arranged in a sheetform in accordance with a predetermined pattern, the sheet is setbetween two thin silicone rubber sheets reinforced with glass fibers,and the resultant is then vulcanized, or a sheet heater formed in such amanner that a coating layer of resistor is formed on a heat resistantresin substrate and the surface is covered by an electrically insulatinglayer. The heating body has the thickness of about from 0.5 to 2 mm andis arranged to obtain a uniform temperature distribution with supply ofan electric current. Shafts 364 are fixed to the both side edges of theflexible sheet heating body 360 throughout a predetermined length fromthe lower end portion by means of screwing, and rollers 365 are attachedas rotatable each to the tips of the shafts 364. The rollers 365 areguided in the guide grooves 376 of sheet heating body guide rails 370,as shown in FIG. 31. Further, guide members which are guided as notrotating but sliding in the guide grooves may be used in place of therollers 365. A most preferable form of the sheet heating body 360 is asheet of continuous body having flexibility as a whole. However, inaddition thereto, another form applicable may be a body having such astructure that hinges connect heating bodies, each comprised of arectangular rigid plate elongate in the direction (the widthwisedirection) perpendicular to the heater feed direction and short inlength in the sheet feed direction.

According to the present embodiment as described above, the pair ofguide grooves 382 are formed in the curved grooves 330a on the surfaceof the female die, and the decoration sheet 315 is curved along thegrooves 330a by inserting the sheet pinching means 388 into the sheetguide grooves 382, whereby the decoration sheet 315 can be adhered moresmoothly to the cavity surface 331a of the female die 330 in the shapehaving the level difference smaller than that of the cavity shape andthe curvature equal to or smaller than that of the cavity shape. Thenpremolding is started from this curved state. Because of this, both thedeformation amount (stretching amount) and the stretching speed becomesmall in the premolding in which the decoration sheet 315 is adhered tothe cavity surface 331a of the female die 330. Accordingly, local stresson the decoration sheet 315 is well dispersed over the entire sheet tobe relaxed, as compared with the cases of premolding performed at astretch from the flat surface to the cavity surface 331a, which makesrare extreme local distortion or breakage of the decoration sheet 315and which can prevent distortion or deformation of the pattern or thelike deposited on the molded article Q.

Further, the above embodiment showed the example where the sheetpinching means 388 was sent downward in the vertical direction from thesheet pinching means feed roll 390 (see FIG. 30), but, without having tobe restricted to this case, it is also conceivable that, as shown inFIG. 43A and FIG. 43B, the sheet pinching means 388 is fed outsubstantially in the horizontal direction from the sheet pinching meansfeed roll 390, the sheet pinching means 388 is advanced along bent sheetguide rails 394, and then it is inserted into the sheet guide grooves382 of the female die 330.

Further, although the embodiment showed the example in which theposition sensor 383 for detecting the predetermined position of thedecoration sheet 315 was provided, the position sensor 383 may beomitted where the pattern on the decoration sheet 315 does not requirepositioning. Further, the operation to open and close the pair ofpinching members 388a, 388a of the sheet pinching means 388 may also becarried out by attraction and repulsion of an electromagnet.

Further, the embodiment showed the example in which the sheet pinchingmeans 388 was connected to the wires 387, but, without having to belimited to this example, chains may be used instead of the wires 387.

Furthermore, the rollers 389 of the sheet pinching means 388 may bereplaced by non-rotating discs, bearings, or the like.

Yet furthermore, the embodiment showed the example where the shapes ofthe cavity surface 331a and the grooves 330a of the female die 330, andof the projections 350a of the sheet clamp 350 were semicylindrical withthe center axis on the x axis (FIG. 30), but they may be semicylindricalwith the center axis on the z axis. The shapes of the grooves 330a andthe projections 350a may be selected from an elliptic cylinder, ahyperbolic cylinder, etc. as well as a cylinder.

Although the embodiment showed the example where the sheet heating body360 was inserted into the sheet clamp 350 at the same time as supply ofthe decoration sheet 315 to the cavity 331 of the female die 330, thesheet heating body 360 may be inserted into the sheet clamp 350 afterthe decoration sheet 315 is supplied to the cavity 331 of the female die330 and then the decoration sheet 315 is pinched between the female die330 and the sheet clamp 350. Further, the decoration sheet 315 used maybe either a bonded and layered laminate film or a transfer film.Further, the injection molding method includes, in addition to themethod wherein a molten resin is injected and cooled to solidify, thereactive injection molding method wherein a resin solution, which is aliquid at room temperature and which is cured by a chemical reaction, isinjected and is cured by the chemical reaction.

According to the present invention, as described above, the decorationsheet 315 can be first curved in a curved state substantially along thecavity surface 331a. Next, after the decoration sheet 315 is heated bythe sheet heating body 360 while retaining it relative to the female die330, the decoration sheet 315 can be smoothly brought into fit to thecavity surface 331a. Namely, premolding is achieved in two steps.Therefore, even though a molding article has the shape with large leveldifference and curvature of the cavity surface 331a in bringing thedecoration sheet 315 into fit to the cavity surface 331a, ahigh-precision injection molded product can be attained withoutdistortion or breakage of the pattern of the decoration sheet 315.

What is claimed is:
 1. A process for effecting injection-molded-in foildecoration, comprising the steps of:deforming a decoration sheet by asheet clamp relative to a female die so that the decoration sheet iscurved substantially along a surface of a cavity of the female die, butis not in contact with the surface of the cavity of the female die,wherein the sheet clamp has a shape corresponding to that of the cavitysurface of the female die; retaining the decoration sheet curvedsubstantially along the surface of the cavity of the female die, betweenthe sheet clamp and the female die; then, heating the decoration sheetby a hot platen having a heating surface of substantially the same shapeas the decoration sheet retained between the sheet clamp and the femaledie, while retaining the decoration sheet between the female die and thesheet clamp so that the decoration sheet is curved substantially alongthe surface of the cavity but is not in contact with the surface of thecavity wherein the retained decoration sheet is softened; fitting saidsoftened and retained decoration sheet closely to the surface of thecavity of the female die; coupling the female die having said softenedand retained decoration sheet closely fitted thereto with a male die toclamp the dies; and injection molding a molten resin between saidsoftened and retained decoration sheet and the male die, therebyadhering the decoration sheet to an injection molded article.